It is the aim of the proposed research to characterize nucleotide sequences in ribosomal RNA (rRNA) both in terms of spatial and functional relationships. Knowledge of the role of rRNA within the ribosome is a prerequisite for complete understanding of protein synthesis, a process common to living organisms of all degrees of complexity and development. It is necessary to fully understand basic life processes such as these so that we may then see how they are altered in pathological and neoplastic cases. We have shown that regions of rRNA are conserved during evolution, by methods of RNA-DNA hybridization and comparative sequence analysis. We plan to further characterize these invariant regions in terms of their primary structural location (by electron microscopy of spread nucleic acids, and by nucleic acid sequence comparison), their secondary structure (by gel electrophoresis isolation of hairpin loops), and their tertiary location in the ribosome. Whether or not invariant regions also occur in transcribed spacers of precursor rRNA, and the polarity of 18S and 28S rRNA within precursor rRNA will also be studied.